Resonant length of longitudinal slots and validity of circuit representation: Theory and experiment

Pertinent theory for the design of longitudinal slot arrays is reviewed and its dependence on the dominant mode scattering off a single slot is pinpointed. The critical need to know resonant length versus slot offset is emphasized and the desirability of determining this information theoretically rather than experimentally is argued. Then method of moments solutions are used to calculate resonant length versus slot offset for given waveguide dimensions and frequency. These theoretical results are compared to new, carefully obtained experimental data. Agreement is found to be so good, it is concluded that one can dispense with the costly gathering of experimental input data when designing longitudinal slot arrays fed by standard rectangular waveguide. A critical look is taken at the validity of representing the longitudinal slot as a shunt element on an equivalent transmission line. This assumption is found to be more and more questionable as thebdimension is reduced. For quarter-height guide, an alternate design procedure is suggested as being more accurate.     

Tuneable and dual-band circular microstrip antenna with stubs

A circular microstrip antenna loaded along its feed axis with either one stub or two stubs has been analyzed using an improved linear transmission line model. When the length of the stub is small, the frequency is tuned over a 9% range in the L-band and, when it is comparable to λ/4, it exhibits dual-frequency operation. The experimental results are in good agreement with the theoretical results     

高速电路非均匀互连线间电磁干扰分析

根据高速电路中线宽发生变化的非均匀互连线结构特点,利用分段线性和等效电路摸型的方法,结合HSPICE电路分析软件,提出了适用于任意条数的非均匀互连线的多导体等效电路模型及仿真模型,从倾斜角度、非均匀互连线长度和信号上升时间几个特殊因素方面,对高速电路中非均匀互连线间的电磁干扰规律进行了分析和总结。     

Modelling of coupled interconnect lines for integrated circuits

A coupled interconnect model is developed using even mode and odd mode capacitance analysis. Signal coupling is presented in terms of interconnect width, substrate thickness, interconnect line spacing, and frequency. Picosecond photoconductor based measurements of coupled transmission lines on the integrated circuit support the even and odd mode signal transmission simulation results. SPICE circuit simulation is used to demonstrate the model utility and explore the sensitivity of the self- and mutual capacitances and inductances in signal crosstalk.     

Theory of traveling-wave transistors

A distributed FET is treated as a problem of coupled active transmission lines over which the traveling waves grow by interaction. Models and equivalent circuits are proposed for evaluation of line parameters and propagation constants. Our calculations show that: 1) the gain increases with transistor width (or length of transmission line) up to about 2 cm, 2) at 15 GHz, a gain of 9 dB is achievable, and 3) the 3-dB bandwidth could be as large as 15 GHz. Possible applications of both types of traveling-wave transistors, unipolar and bipolar are discussed.     

Characterization of MIS structure coplanar transmission lines forinvestigation of signal propagation in integrated circuits

A full-wave analysis of metal-insulator-semiconductor (MIS) structure micron coplanar transmission lines on doped semiconductor substrates is carried out using a finite-difference time-domain approach. Metal conductor loss is taken into account in the analysis. Line parameters and electromagnetic field distributions are calculated over a wide frequency range involving slow-wave and dielectric quasi-transverse-electromagnetic mode limits. Measurements of these line parameters, varying substrate resistivity from 1 to 1000 Ω-cm, in the frequency range up to 40 GHz are also presented, and these agree with the analysis quite well. On the basis of these results, an equivalent circuit line model is induced and some considerations on the relationship between line structure and properties made     

Analysis of a slot microstrip antenna

The slot microstrip antenna is used as a folded slot dipole symmetrically fed across a gap by means of a strip line. A theoretical model equivalent to several lossy transmission lines had been described previously to explain the bandwidth and the radiation admittance. The theory is improved when coupling between the two equivalent radiating lines of every slot is taken into account, and explains a fourth resonance near the third one, which had been measured on several models. Theoretical results and experiments are in good agreement. They are radiation admittance in a wide frequency band, current distribution along each slot and radiation patterns.     

并行传输线共模泄漏的等效场-线耦合数值模型

针对并行传输线间感性和容性耦合计算问题,该文提出并行传输线等效场-线耦合亚网格时域有限差分(FDTD)数值模型,模型更适合非均匀介质等复杂情形的耦合串扰求解,且具有更为简洁的数值计算形式。利用该等效场-线耦合数值模型,对并行传输线间共模电磁信息泄漏进行模拟仿真和实验测试,时域模拟和频域实验结果均表明,该模型可以有效刻画并行传输线共模电磁信息泄漏发射特性。     

大栅宽功率器件的分布性研究

随着器件工作频率的升高,以集总元件模型描述大栅宽功率器件引入的误差将越来越大,且这一趋势随着栅长的减小更加显著。对微波大栅宽功率器件的分布性作了初步研究,对传统建模和器件优化方法进行改进,将器件中的有源部分和无源部分分离开,利用微波传输线理论和奇偶模分析对器件的无源部分建模,在满足集总条件时对有源区建模,将两者综合建立了分段的线性模型。与测量结果进行了比较,表明分段模型取得了更为精确的结果;在此基础上又建立了分段的非线性模型,模拟和验证了大栅宽器件的早期非线性现象;最后还提出了功率器件栅宽优化设计的估算方法。     

Analysis and network modeling of an aperture-coupled microstrippatch antenna

This paper describes a method for analyzing an aperture-coupled microstrip patch antenna in order to develop an improved transmission-line model that reflects the effects of structure parameters, including inclination angles and offset distances of the aperture with respect to the feed line or the patch. The equivalent circuit consists of three ideal transformers, extended slotlines terminated by a short circuit, and microstrip transmission lines with open stubs. Two transformers are introduced to take account of the interaction between the aperture field and two orthogonal patch modes, while the third transformer reflects the coupling between the aperture and the feed line. The turn ratios of the transformers are calculated efficiently. The microstrip open stubs in the patch are then replaced by well-known capacitance and radiation conductance equivalents. The proposed transmission-line model is then applied to several variations and shown to produce accurate antenna impedances     

Tunable microwave oscillators employing narrowband MSSW delay lines

A recently reported experimental study of microwave tunable oscillators employing narrowband magnetostatic-wave (MSW) delay lines is reviewed. The narrowbanding was achieved by usinglifted transducers with magnetostatic surface waves (MSSWs) which yielded a bandwidth of 10 MHz with an insertion loss of less than 20dB. This approach at delay-line narrowbanding does not work as well with the other MSW wave-types because of increased insertion loss. The mode-hopping problem which beset earlier studies of MSW delay-line oscillators was overcome in the present work but now a different problem arose, viz., frequency jumping, which occurred every time the electrical length of the circuit external to the delay line changed by 360 degrees. A maximum tuning range of about 600 MHz was obtained, with this range limited primarily by the Avantek GaAs FET amplifier that was used whose electrical length was equivalent to about 45 cm of air transmission line. It was concluded that, if the electrical length of the external circuit is sufficiently reduced (ideally made zero), singlemode operation over an octave bandwidth or more is possible.     

Nonuniformly coupled microstrip transversal filters for analog signal processing

The Fourier transform relationship between frequency response and impedance profile for single nonuniform transmission lines is used to derive the time-domain step response of single and coupled nonuniform lines. The expression for the step response of a characteristically terminated nonuniformly coupled transmission line structure is shown to correspond to the characteristic impedance profile. By using this relationship, any arbitrary step response can be realizing by utilizing nonuniformly coupled strip or microstrip lines for possible applications as waveform-shaping networks and chirp filters. A numerical procedure to compute the step response of the nonuniform coupled line four-port is also formulated in terms of frequency-domain parameters of an equivalent cascaded uniform coupled line model with a large number of sections. Sinusoidal and chirp responses are presented as examples that are readily implemented using coupling microstrip structures. The step response of an experimental nonuniformly coupled microstrip structure is presented to validate the theoretical results.<>     

Accurate characterization of planar printed antennas usingfinite-difference time-domain method

The finite-difference-time-domain method (FD-TD) is used to characterize complex planar printed antennas with various feed structures, which include coaxial probe feed, microstrip line feed, and aperture coupled feed structures. A coaxial probe model is developed by using a three-dimensional FD-TD technique. This model is shown to be an efficient and accurate tool for modeling coaxial line fed structures. A novel use of a dispersive absorbing boundary condition is presented for a printed antenna with a high dielectric constant. All the numerical results obtained by the FD-TD method are compared with experimental results, and the comparison shows excellent agreement over a wide frequency band     

A Compact Slot Antenna Utilizing a Right/Left-Handed Transmission Line Feed

A novel compact planar antenna utilizing cascaded right/left-handed transmission lines is proposed. The significance of layout planning with respect to radiation is investigated and discussed in this paper. Two segments of transmission lines of the same electrical length with opposite signs are cascaded to provide zero phase at the operation frequency. The closed-form formulas for the equivalent circuit of a transmission line are used for circuit design. Both antenna layout and radiation mechanism are discussed. For experimental demonstration, the proposed antenna operating at 2.45 GHz was implemented on an FR4 substrate. The topology using several patches has quite smaller size than the conventional patch antenna. Besides, a fairly omnidirectional radiation pattern was measured.     

一种抑制差分拐角共模噪声的补偿模型

为抑制差分传输线拐角处不对称造成的共模噪声,文中提出了一种新的45°拐角差分传输线补偿模型。该模型通过对差分拐角造成的线长差进行有效补偿,利用HFSS和ADS进行建模仿真,从时域和频域进行验证。结果证明,从S参数来看,其有效地将频率8 GHz处的差模转共模噪声降低了20 dB,同时降低了差模插入损耗;从时域来看,共模噪声比之前减小了大约90%。     

Beam squint in axially symmetric reflector antennas with laterallydisplaced feeds

Numerical calculations have been carried out and the beam squint for circular polarized excitation has been measured using a 100 m telescope. The telescope was operated in the Gregorian mode, where the equivalent focal length equals 387.5 m. The feed horn was laterally displaced by 1.364 m from the optical axis at the system focus. Good agreement was obtained between the numerical calculations and the experimental results. The authors found a shift of the two radiation patterns of ≃2 arcsec. The orientation of the beam squint in the configuration with a laterally displaced feed is different from the orientation in offset reflector antennas     

微带线不连续性对光电导开关非线性特性的影响

实验对自行研制的全固态同轴―微带型横向半绝缘砷化镓(SI-GaAs)光电导开关传输特性进行了研究：当偏置电压达到一定阈值时,普通开关进入了非线性锁定（Lock-on）工作模式;在相同实验条件下,当微带线出现不连续时,输出的电脉冲波形没有出现锁定现象;分别用空气击穿的流注模型和微带线等效电容机理分析了微带线不连续效应引起整个开关电路性能变化及抑制开关Lock-on效应的原因。     

Transmission characteristics of finite-width conductor-backedcoplanar waveguide

This paper presents theoretical and experimental results for a finite-width conductor-backed coplanar waveguide (FW-CBCPW). The guiding characteristics of FW-CBCPW are investigated first by the rigorous method of mode matching. An FW-CBCPW through line is then placed within a test fixture commonly used in laboratories, and the scattering parameters of the through line are obtained theoretically by approximating the FW-CBCPW as a simple system of coupled transmission lines. Experimental results are shown to agree very well with the theoretical ones. In particular, the anomalous behavior observed in the transmission characteristic of the through line is related to the resonant phenomenon of the terminated side planes which are short-circuited at both input and output ends due to the test fixture. Finally, a technique of mode suppression in the side-plane regions is suggested for the improvement of signal transmission over a broad band of frequency spectrum. The effects of extra higher order modes on the transmission characteristics at high frequencies are also discussed     

UHF Backward-Wave Parametric Amplifier

This paper describes a breadboard model of a UHF varactor diode backward-wave parametric amplifier that can be electronically tuned over an octave tuning range (250-500 Mc). It operates in a mode that has a relatively constant idler frequency; however, it uses two forward-wave transmission lines in contrast to the backward-wave transmission line requirement previously reported. A theoretical discussion on the design considerations of this mode is presented and applied to the UHF model. Measurements taken in the conventional mode of operation (output frequency equal to the input frequency) yielded voltage gain bandwidth products in excess of 100 Mc and over-all effective receiver noise temperatures of less than 140/spl deg/k. Detailed measurements in the mode where the constant idler frequency is used as the output were not taken because directional filters and circulators, which are necessary in this mode, were not available.     

Simulation diagnostics of multiple discontinuities in a microwavecoaxial transmission line

Multiple discontinuities in microwave transmission lines can cause unusual reflection and transmission loss characteristics as functions of frequency. This article presents a method for developing models that simulate return loss and insertion loss data measured over a broad band of frequencies. The overall cable is modeled as a coaxial transmission line consisting of shunt susceptance discontinuities separated by line lengths. A nonlinear least-squares fit is then performed between theoretical data (from the model) and experimental data. When this method was applied to modeling discontinuities in a slightly damaged S-band antenna cable, excellent agreement between theory and experiment was obtained over a frequency range of 1.70-2.85 GHz